How to Change the Magneto on a Briggs & Stratton

A Briggs & Stratton lawn mower engine utilizes a magneto coil to generate spark for the spark plug.
A Briggs & Stratton lawn mower engine utilizes a magneto coil to generate spark for the spark plug. (Image: Comstock/Comstock/Getty Images)

Briggs & Stratton is a small-engine manufacturer whose engines are commonly found on lawn and garden equipment such as lawn mowers, snow throwers, tillers and more. On older Briggs & Stratton engines, the ignition required points and a condenser to generate spark for the spark plug. However, newer engines utilize a solid-state magneto ignition coil. If your Briggs & Stratton engine has no spark, you may need to change the engine's magneto.

Things You'll Need

  • Socket set
  • Briggs ignition module
  • Flexible 0.015-inch feeler gauge

Disconnect the spark plug wire from the spark plug by pulling firmly on the black rubber boot at the tip of the spark plug.

Loosen the three bolts that hold the starter housing on top of the engine, using a socket set, and lift the housing up and off the engine. Set the housing and the bolts aside.

Rotate the flywheel so that the magnets are on the opposite side of the flywheel from the magneto.

Loosen the two bolts that hold the magneto onto the engine next to the flywheel. Lift the magneto and the spark plug wire out of the engine compartment.

Place the new magneto into the engine compartment and route the spark plug wire in the same way the previous unit was removed. Hand-tighten the screws to hold the magneto in position.

Place a flexible 0.015-inch feeler gauge between the flywheel and the magneto. Press the magneto firmly against the flywheel, to ensure that the gap between the two (with the pinched feeler gauge) is exactly 0.015 inch. Tighten the two bolts to hold the magneto in position.

Remove the feeler gauge and rotate the flywheel so the magnets are against the magneto, and check the gap once again. If the bolts were properly tightened, the gap should still be 0.015 inch.

Replace the starter housing, and secure it by tightening the three bolts. Reconnect the spark plug wire to the spark plug and start the engine.

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